Lung cancer is the third most common site of origin of metastatic cancer
deposits in bone, after breast and prostate cancer. Patients are
usually over 40, and the average age is around 55. A smoking history
is almost always present.
Patients may have no other manifestation of cancer other than their painful
bone lesion. When a patient has a metastasis and no site of origin
can be found (a metastasis of unknown origin) the most likely site
is the lung or kidney.

Pain is the most common presenting symptom. Pathological fracture
rarely occurs without a history of a few weeks or months of increasingly
severe pain. In some cases the patient has tried to ignore or deny
the symptoms. Sometimes a painful bone lesion is thought to be a
"muscle pull" or a "sprain" and strong pain medicines
are prescribed, allowing the patient to continue to tolerate very severe
pain before the true nature of the problem is discovered. Systemic symptoms
may also occur, such as hypercalcemia and hypertrophic pulmonary osteoarthropathy
(painful thickening of the long and short tubular bones and clubbing of
the fingers).

Lung cancer metastasis most commonly affects the spine, ribs, pelvis,
and proximal long bones. A unique feature of this lesion is its
ability to spread to the bones of the hands and feet. Half of all mets
to the hand bones are from lung, as well as 15% of lesions in the
feet. This is thought to be due to the ability of a tumor in the
lung to shed malignant cells directly into the arterial blood flow, from
where they can be seeded far and wide. Other tumors shed cells into the
veins, from which they go first to the lung or liver, which may act as
filters and trap metastatic cells.

Lung cancer metastases normally appear purely lytic, with poor margination,
no matrix and cortical destruction. Lung lesions in bone may also
be blastic. When you see a smoker over age 40 with multiple bone
lesions, think lung cancer.

Lung cancer with metastasis to bone is one of the most aggressive tumors
and has a very unfavorable prognosis. The average survival after
the diagnosis of a met is about 6 months. However, a few selected
cases have been associated with prolonged survival with appropriate treatment.
There is virtually no role of curative surgery. Orthopedic stabilization
of weakened bones should be done promptly, before fractures can occur.
Patients should receive complete treatment according to their wishes and
the extent of the disease. Orthopaedic stabilization of actual or
impending pathological fractures should not be withheld unless the patient
cannot tolerate anaesthesia or would definitely not be benefited by surgery.
The pain relief from stabilization of damaged bones may warrant surgical
treatment even if the patient cannot enjoy a functional benefit, such
as increased walking ability.